ECM Hydrogels for Regenerative Medicine

The ECM is a highly complex mix of structural and functional proteins and other biomolecules. These molecules are secreted by the cellsCells resident in every tissue in the body but can also influence their behavior through a process of “dynamic reciprocity.” As a result, there has been significant interest in utilizing ECM as a biologic scaffold material in tissue repair and replacement. Numerous preclinical and clinical studies have demonstrated the efficacy of ECM biomaterialsBiomaterials , and more than 4 million patients have now been treated with these scaffold materials. The discovery that these materials could be formed into hydrogelsHydrogels promised to further expand their clinical utility by offering minimally invasive delivery and the ability to fill irregularly shaped defects. This chapter will briefly outline the history and characterization of ECM biomaterialsBiomaterials and their evolution from single sheet to multisheet, powder, and ultimately hydrogelHydrogel form. The first studies describing the production of early-generation ECM hydrogels used well-characterized porcine small intestinal submucosaSmall intestinal submucosa and urinary bladder matrixUrinary bladder matrix , and these materials will be discussed in the context of the general methods used to produce and characterize ECM hydrogels. A detailed consideration of the many second-generation hydrogels which have since been produced from a wide range of tissues will then be discussed in the context of tissue specificityTissue specificity . The hydrogels discussed in this chapter have been evaluated in vitro or in small scale in vivo animal studies. More substantial evaluation is required before these materials can be considered ready for clinical application, but these hydrogelsHydrogels provide the possibility for minimally invasive delivery, treatment of irregularly shaped defects in anatomic sites that prove challenging for invasive surgical procedures, and may provide an ECM formation that delivers immediate bioactivity as a consequence of its distinctive biomolecular composition.